【作者】 徐海斌；

【导师】 沈永行；

【作者基本信息】 浙江大学 ， 光学工程， 2011， 博士

【摘要】 随着大量优良品质非线性晶体的涌现及外加电场周期性畴极化技术的成熟,非线性光参量放大及振荡成为实现宽波段激光可调谐输出的主要技术手段。非线性光参量变换技术的研究得到了越来越多激光研究人员的关注。以市场上成熟的高功率固体激光器作为泵浦源,通过非线性光参量放大及振荡,可以实现中、远红外波段可调谐激光输出。该波段激光在光电对抗、红外干扰、激光雷达、环境检测、医疗等领域均具有重要的作用。本论文主要对宽带泵浦非线性光参量放大及振荡进行研究,获得了宽带泵浦下参量光谱带宽及增益特性,给出了描述参量光谱带宽特性的一般数学表达式。同时,本论文采用英国SPI公司的光纤激光器作为泵源,以5mol％PPMgLN晶片作为非线性工作介质,实现了1410 nm～1620 nm可调谐信号光振荡输出,并对信号光的带宽特性和功率特性进行了研究。本论文主要工作包括以下几个方面：单色泵浦光参量放大调谐特性及容差特性的研究；宽带泵浦光参量放大光谱带宽特性及增益特性的研究；对宽带泵浦光参量振荡的实验研究。光参量放大调谐及容差特性的研究对实现高效非线性光频转换具有重要的意义。本论文通过对非线性三波耦合位相失配函数的泰勒展开,对单色泵浦光参量放大的调谐及容差特性进行了系统的研究。研究首次发现,参量光波长具有一个泵浦波带宽压缩点。在该压缩点附近,参量光波长具有最大的泵浦波长接受带宽。该研究也有利于实现泵浦波长漂移的参量光波长稳定输出。宽带泵浦光参量放大及振荡在级联光参量振荡及宽带光放大领域具有重要的应用,而相关的理论研究却鲜有报道。本论文对宽带泵浦光参量放大的带宽及增益特性进行了研究,发现泵浦带宽放大系数随着参量光波长输出位置、非共线角和温度等因素而发生变化,在参量光波长的压缩点附近参量光波长具有最窄的光谱带宽及最大的增益。论文最后以英国SPI公司的脉冲光纤激光器作为宽带泵浦,采用研究组自行研制的5mol％PPMgLN晶片,开展光参量振荡实验研究。当泵浦脉冲频谱带宽约为6.2 nm,时域带宽约为10～20 ns时,获得信号光波段在1410 nm～1620 nm的参量光波长的频谱带宽及输出功率。通过对光参量振荡信号光输出功率特性的研究,我们发现中心泵浦波长为1.062μm时,在参量光波长1530 nm位置附近能够获得最大的输出功率,而在偏离1530 nm区域,参量光输出能量则逐渐减小,该结论与理论模拟所获得的宽带泵浦光参量放大增益特性的结果完全一致。更多还原

【Abstract】 With the development of a large number of good quality nonlinear crystals and the electric field domain poling technique, nonlinear optical parametric amplification and oscillation become the main-stream technique in achieving broadband wavelength tunable laser output, which is impossible for common solid-state lasers. More and more researchers have been focusing on the study of nonlinear optical parametric conversion technology. With the mature high-power solid-state laser as the pump source, the mid-infrared and far-infrared band tunable laser output can be achieved, through nonlinear optical parametric amplification and oscillation. These lasers have important roles in optoelectronic counter measurement, infrared jamming, laser radar, environmental test, medical treatment and other fields. This thesis focuses on the study of broadband pumped nonlinear optical parametric amplification and oscillation. The characteristics of spectral bandwidth and gain are analyzed. The general mathematical expression to describe spectral bandwidth is given out. Optical parametric oscillation pumped with a broadband pulsed fiber laser is experimentally demonstrated. The 5mol% doping PPMgLN is used as nonlinear crystal. The parametric output wavelength tunable from 1410 nm to 1620 nm is obtained. Spectral bandwidth and power characteristics are investigated.This thesis includes the following three parts:(1) Investigation on the tunability and the tolerance of optical parametric amplification based on monochromatic pump; (2) Study of spectral bandwidth and the gain properties based on the broadband pumped optical parametric amplification; (3) Experimental investigation on the broadband pumped optical parametric oscillation.Tunability and tolerance of optical parametric amplification is of great significance in achieving efficient nonlinear optical frequency conversion. Based on the monochromatic pump optical parametric amplification, the tunability and tolerance characteristics are systematically studied, through Taylor expansion of nonlinear phase mismatch function in three-wave coupling process. It is first found that there exists a compression point in parametric output wavelength toward pump bandwidth. Parametric output wavelength possesses the largest pump acceptant bandwidth near the compression point. Parametric output wavelength is stable even with drifting pump wavelength near the compression.Broadband pump optical parametric amplification and oscillation have important applications in the cascaded optical parametric oscillation and the broadband optical parametric amplification. However, related theoretical studies have rarely been reported. In this thesis, the spectral bandwidth and the gain characteristics are investigated for the broadband pumped optical parametric amplification. We find that the amplification factor of the pump bandwidth varies with the parametric wavelength, the noncollinear angle and temperature. Parametric wave possesses the narrowest spectral and the largest gain near the compression point.Finally, optical parametric oscillator pumped with a pulsed SPI fiber laser is experimentally demonstrated. The laser is 6.2 nm in bandwidth with a pulse duration between 10 and 20 ns. Parametric wavelength ranging from 1410 nm to 1620 nm are achieved. The spectral bandwidth and the power properties are investigated. Through experimental study, we find the highest power output is near 1530 nm. When the parametric output wavelength deviated from 1530 nm,the output power decreases gradually. The conclusion is in good accordance with the theoretical analysis and numerical simulations.更多还原